Semiconductor devices are used in many electronic and other applications. Semiconductor devices comprise integrated circuits or discrete devices that are formed on semiconductor wafers by depositing many types of thin films of material over the semiconductor wafers, and patterning the thin films of material to form the integrated circuits.
Electronic switches, such as MOSFETs, IGBTs, or other types of transistors are widely used as electronic switches for switching electrical loads, such as motors, lamps, magnetic valves, and the like. In these applications, the electronic switch is connected in series with the load, where the series circuit with the electronic switch and the load is connected between power supply terminals. The load can be switched on and off by switching the electronic switch on and off.
The load current or the current flowing through the electronic switch is a critical parameter in many applications. This current is measured indirectly by measuring a current through a sense transistor. The sense transistor is biased similar to the main switching transistor but is much smaller in size than the main or load transistor. The load current is obtained by scaling the sense transistor using a suitable scaling algorithm. However, because of various differences between the sense transistor and the main transistor, the ratio of the current flowing through the sense transistor and the main transistor may change during operation and at different operating conditions. Such variations can result in significant variation or error in the computed load current resulting in disastrous consequences.